How can I easily simplify a derivative of sin^-1 (2x + 1)?

In summary, the conversation involves finding the derivative of sin^-1 (2x+1) and simplifying the answer to get the final answer. The conversation also includes a discussion on pulling a 2 out from under a radical in the equation.
  • #1
communitycoll
45
0

Homework Statement


Find derivative of sin^-1 (2x + 1)


Homework Equations


I do everything Wolfram does except I don't know how to simplify to get the final answer.

http://www.wolframalpha.com/input/?i=derivative+sin^-1+(2x+++1)


The Attempt at a Solution


Everything Wolfram does basically.
 
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  • #2
I don't see how you can expect anyone to tell you how to simplify what you got to Wolfram's formula, if you don't tell us what you got!
 
  • #3
Ah terribly sorry. 2 / sqrt(1 - (2x + 1)^2); the last thing in the show steps part for the derivative in Wolfram.
 
  • #4
Of course, you know that (2x+1)^2= 4x^2+ 4x+ 1. That means 1- (2x+1)^2= 1 -4x^2- 4x- 1= -4x^2- 4x= -4(x^2- x)= -4x(x-1).
 
  • #5
HallsofIvy said:
Of course, you know that (2x+1)^2= 4x^2+ 4x+ 1. That means 1- (2x+1)^2= 1 -4x^2- 4x- 1= -4x^2- 4x= -4(x^2- x)= -4x(x-1).

But if -4x(x-1) is under a radical (as well as being multiplied) how is it that I pull a 2 out of that?
 
  • #6
communitycoll said:
But if -4x(x-1) is under a radical (as well as being multiplied) how is it that I pull a 2 out of that?

[itex]\sqrt{-4x(x-1)} = \sqrt{4 \cdot -x(x-1)} = \sqrt{4} \sqrt{-x(x-1)} = 2\sqrt{-x(x-1)}[/itex]

It should be noted [itex]1 - (2x + 1)^2 = -4x(x+1)[/itex]. I'll leave it to you to show [itex]\sqrt{-4x(x+1)} = 2\sqrt{-x(x+1)}[/itex].
 
Last edited:
  • #7
communitycoll said:
But if -4x(x-1) is under a radical (as well as being multiplied) how is it that I pull a 2 out of that?
What, exactly, do you think the square root of 4 is?
 
  • #8
Ah. I understand now. It took me a bit, but I understand now. Thanks.
 

Related to How can I easily simplify a derivative of sin^-1 (2x + 1)?

1. What is a derivative?

A derivative is a mathematical concept that describes the rate of change of a function at a specific point. It represents the slope of the tangent line to the function at that point.

2. Why do we simplify derivatives?

We simplify derivatives in order to make them easier to understand and work with. Simplifying a derivative can also help us to find the critical points and extrema of a function.

3. How do we simplify a derivative?

To simplify a derivative, we use mathematical rules and properties, such as the power rule, product rule, quotient rule, and chain rule. We also use basic algebraic techniques, such as factoring and combining like terms.

4. Can all derivatives be simplified?

No, not all derivatives can be simplified. Some derivatives, such as those involving trigonometric or exponential functions, may require more advanced techniques to simplify.

5. Why is it important to understand how to simplify derivatives?

Understanding how to simplify derivatives is important because it allows us to analyze and solve complex problems involving rates of change and optimization. It also provides a foundation for higher level math concepts, such as integration and differential equations.

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